It is known from EP 1 413 045 B1 and corresponding U.S. Pat. No. 7,068,191, KUNER & SCHONDELMAIER, to control electric motors using pulse width modulation (PWM). The control pulses are, in this context, applied to the motor in the form of a PWM signal having a constant clock frequency (period length T=constant). The duration t of the current pulses or associated pulse off-times (T−t) is variable; the rotation speed of the motor is specified by the pulse duty factor t/T of the PWM signal. A change in the pulse duty factor t/T correspondingly produces a change in the rotation speed.
Whereas rotation speed control of the electric motor can be performed using a suitable PWM signal, data that must likewise be transferred to the motor while it is in operation, for example a desired rotation direction, must (according to the prior art) be transferred to the motor via an additional lead.